Plug-in section for bus duct



p 1965 J. B. CATALDO ETAL 3,206,706

PLUG-IN SECTION FOR BUS 'DUCT Original Filed May 25, 1959 2 Sheets-Sheet2 INVENTORS JU/V/V 6. (47/1100 United States Patent 3,206,706 PLUG-INSECTION FOR BUS DUCT John B. Cataldo, Bloomfield Hills, Robert W.Thomas, St. Clair Shores, and Michael L. Mead, Detroit, Mich., assignorsto I-T-E (Iircuit Breaker Company, Philadelphia, Pan, a corporation ofPennsylvania Original application May 25, 1959, Ser. No.'8l5,562.Divided and this application Get. 11, 1962, Ser.

No. zzasrs ci. 3s9 22 2 Claims.

This application is a division of copending application Serial No.815,562, filed May 25, 1959, now abandoned.

The instant invention generally relates to electrical distributionsystems comprising bus ducts and more particularly to a novel bus ductconstruction whereby the tapping of electrical energy from the bus ismade in a safe manner.

Bus ducts comprising a plurality of spaced parallel conductors disposedwithin an elongated housing are described in detail in the J. B. Cataldocopending application Serial No. 772,814, filed November 10, 1958,entitled Clamped Busway Structure, now U.S. Patent 3,088,994, issued May7, 1963, and assigned to the assignee of the instant invention. Openingsare provided in the bus duct housing spaced at intervals along thelength thereof whereby electrical energy may be tapped from the bus ductconductors by means of contact fingers which are part of a plug unit ofthe type illustrated in the W. H. Frank et al. copending applicationSerial No. 637,575, filed January 31, 1957, entitled Bus Duct Plugs WithCover Operated Retractable Contact Fingers, now U.S. Patent 2,861,139,issued November 18, 1958, and assigned to the assignee of the instantinvention.

The ability of the plug device to tap current from the bus duct dependsupon the successful coordination between the contact fingers of the plugdevice and the conductors of the bus duct. This coordination is usuallyaccomplished by means of contact fingers which engage totally exposedportions of the bus conductors which are positioned opposite the housingopenings. While the contact engagement may be electrically satisfactory,the bared portions of the conductors pose a safety problem.

Experience has shown that during any portion of the sequence ofoperation in installing and removing a plug device, that is, opening theduct door, aligning the plug unit, removing the plug unit, and leavingthe door opened, etc., it is relatively simple to accidentally bridgethe gap between conductors or between a conductor and the duct housingwith a metal object. When such accidental contact is made a power arc isstarted which can severely injure the person installing the plug unitand which also causes extensive damage to the electrical distributionsystem.

The instant invention substantially reduced the probability of suchaccidental occurrences by employing duct conductors which are insulatedat least at the portions thereof which are accessible through the ductopenings and by providing a minimum size opening to receive contactfingers of the plug unit. Thus, the construction of the plug unit may beconsiderably simplified since retractable contact fingers are no longerrequired as a safety feature.

Accordingly, a primary object of the instant invention is to provide anovel bus duct construction having a dead front appearance wherein aminimum of conductor material is exposed so as to substantially decreaseopportunity for accidental shorts developing between conductors andbetween a conductor and the bus enclosure.

Another object is to provide a novel bus duct with the conductorsthereof having pocket means associated there with at the plug-inportions of the duct for receiving and 3,206,706 Patented Sept. 14, 1965surrounding the plug unit contact fingers and acting as the cooperatingcontacts therefor.

Still another object is to provide a novel bus duct having insulatingmeans at the plug-in portions with a small access opening or slit oflesser area than the cross-section of the plug-in contact fingers.

A further object is to provide a novel pocket construction which permitsdeflected insulation to position itself so as not to interfere with thecontact area for the plug-in contact fingers.

A still further object is to provide a novel resilient type pocketconstruction serving as a cooperating contact whereby contact pressureis maintained against a solid type of plug unit contact finger.

Briefly, the device of the instant invention comprises a bus duct unitwherein the conductors are each provided with tap means in the form of apocket positioned at the plug-inareas of the duct with each pocket beingconstructed to receive a plug unit contact finger when the finger is inengagement with the conductor of the bus duct. In this manner power istapped from. the bus duct. The pockets are covered with insulationconstructed of resilient material having an opening aligned with thepocket opening. The insulation opening may comprise a slit or be of anyother desired shape. In any event, the insulation opening isconsiderably smaller than the pocket means opening and is even smallerthan the crosssectional area of the plug unit contact finger.

When the plug unit contact finger is entered into the pocket means theinsulation covering of the pocket means readily deflects and uponwithdrawal of the contact finger the insulation resumes its originalshape wherein the contact areas of the bus conductors cannotaccidentally be contacted.

The objects of the instant invention hereinbefore noted as well as otherobjects will become readily apparent after reading the followingdescription of the accompanying drawings in which:

FIGURE 1 is a side elevation of a fragmentary portion of a bus ductconstructed in accordance with the teachings of the instant invention.

FIGURE 2 is a cross-section taken through line 22 of FIGURE 1 looking inthe direction of the arrows.

FIGURE 3 is a fragmentary side elevation of conductors of a bus ductunit conductor at the plug-in region with the insulating coveringthereof removed.

FIGURE 3A is a plan view of the conductor of FIG- URE 3 looking in thedirection of arrows 3A3A.

FIGURES 4A-4C are plan views of the portion of the conductor illustratedin FIGURE 3, with the insulating covering thereon, illustrating thevarious shapes which the opening of the insulation can assume.

FIGURES 5A-5C are side elevations illustrating three differentconstructions for resilient type plug unit contact fingers.

FIGURE 6A is a cross-section, taken through lines 6A-6A of FIGURE 6Blooking in the direction of the arrows, illustrating a modified pocketconstruction wherein finger type contacts engage both sides of the busconductor.

FIGURE 6B is a cross-section taken through lines 6B-6B of FIGURE 6Alooking in the direction of the arrows.

Now referring to the figures and more particularly to FIGURES 1 and 2,bus duct unit 20 comprises an elongated housing 21 constructed ofU-shaped members 22, 23 at the top and bottom thereof secured to sideplates 24, 25 by screw means 26'. Side plate 25 includes offset portionsat the long edges thereof whereby spaces 26, 27 are formed between sideplate 25 and one arm of U- shaped members 22, 23. Door 28 is disposedwithin spaces 26, 27 so as to be slidable therein.

a Housing 21 is provided with a plurality of longitudinally spacedplug-in openings 29, only one of which is illustrated, in side plate 25.Bus duct unit also includes four parallel conductors -33 disposed withinhousing 21 and maintained in operative position by insulator means 34 ina manner well known to the art.

Each of the conductors 3033 is provided with a pocket means for eachplug-in location defined by a housing opening 29. It is to be noted thatpocket means 35 of conductors 31 and 33 are longitudinally spaced frompocket means 35 of conductors 30 and 32 so as to minimize the size ofhousing openings 29. Thus, it can be said that pocket means 35 of busbars 3033 are positioned in staggered relationship.

Each of the conductors 30-33 are comprised of a first and a secondlaminate 36, 37 which abut one another for substantially the entirelength of bus duct unit 20. The pocket means 35 is formed by outwardlyextending embossed portions 38, 39 of laminates 36, 37, respectively.Conductors 30-33 are covered for the entire lengths thereof by resilientinsulating material 40, in a manner fully explained in the aforesaidcopending application 772,814. Insulation 40 is provided with roundopenings 41 which are aligned with the openings of pockets 35 for areason to be hereinafter explained.

FIGURES 3 and 3A illustrate a conductor 45 formed of laminates 46, 47drawn together by rivets 48. Laminates 46, 47 include outwardlyextending portions 49, 50, respectively which cooperate to form pocket51. Pocket 51 is adapted to receive a resilient type contact finger 52(FIGURE 5A) which comprises two sections 53, 54 of conducting materialjoined by rivet 55. A compression spring 56 disposed within recess 57 ispositioned between members 53, 54 thereby urging these members away fromone another into good electrical contact with the inner surfaces 58, 59,respectively of pocket means 51. Compression spring 56 may be eliminatedin contact fingers of the type illustrated in FIGURES 5B and 5C whichare comprised of material inherently resilient in character.

The formations 49, comprising pocket 51 are adapted to be covered by asleeve 60 (FIGURES 4A-4C) having variously shaped access openings 61a61cthrough which contact finger 52 must pass before entering pocket 51.Pocket means opening 61a is round, pocket means opening 61b is ofelongated shape, and pocket means 610 is a mere slit. It is to be notedthat each of the openings 610-610, in the normal positions thereof,illustrated in FIGURES 4A4C, are considerably smaller in size than theopening which pocket 51. presents to contact finger 52. Thus, when thedoor 28 for the plug-in region opening 29 is opened a dead frontappearance is presented so that the chances of accidentally shorting theconductors of bus duct unit 20 to housing 21 or creating a short betweenconductors is, for all practical purposes, impossible. I

Since the material which forms sleeve 60 is resilient in nature contactfinger 52 when inserted into pocket 51 will enlarge the access openings61a61c and upon withdrawal of contact finger 52 the access openings61a-61c will return to their normal position.

Up to this point, each pocket means described has been considered to beconstructed of rigid material with the parts being fastened securely toeach other. Contact pressure has been obtained by a separate spring inthe plug unit contact fingers (FIGURE 5A) or by making the contactfingers of inherently resilient material either in two sections (FIGURE5B) or by having a single section bent over portion in the form of a Vat the end thereof (FIGURE 5C). However, the pocket formed by theconductors and other members may also be made resilient so as to becapable of accepting solid, stab type contact fingers.

The embodiments of this invention hereinbefore def scribed utilize plugunit contact fingers which make contact against the inside walls of thepocket forming lamimates and parts. It is possible to reverse theconstruction of the pocket means for utilization with clip type contactfingers which engage the bus duct conductors on opposite sides thereof.

FIGURES 6A and 6B illustrate a modification. Pocket means 130, areformed by a ring-like member 131 having diametrically opposed slots 132.Bus bar 133 is entered into slots 132 so as to be positioned along adiameter of ring-like member 131. Sleeve-like resilient in sulator 134is placed over pocket means 130, 130 with the access opening 135 ofinsulator means 134 being in glignment with the entrance opening topocket means 130,

It is to be understood that this invention may be carried out byconstructing the pockets of any given configuration depending upon thesize and contour of the plug unit contact fingers. The insulation meansmay be resilient and continuous. While a tube or sleeve has proven to bethe most practical any form such as sheet, tape, potting compounds orepoxy or plastisol can also be used. However, if desired the insulationcan be both discontinuous and rigid, being confined to the plug inregion of the bus duct unit.

Thus, this invention provides a novel construction for a bus duct unitwhich achieves a substantially dead front appearance, that is, theconductors in the plug-in regions are substantially covered byinsulating material so as to prevent accidental shorts from occurringduring installation and removal of plug units.

Although we have here described preferred embodiment of our novelinvention, many variations and modifications will now be apparent tothose skilled in the art, and we therefore prefer to be limited, not bythe specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. A bus duct comprised of an elongated housing and a plurality oflongitudinally extending electrical conductors disposed within saidhousing; said housing having an opening therein defining a location atwhich power may be tapped from said bus duct by means of a plug unit;pocket means individual to each of said conductors having an openingoperatively positioned in alignment with said housing opening to receiveplug unit contact fingers which engage said conductors; an insulatingmeans, individual to each of said conductors covering its associatedconductor for at least a portion thereof aligned opposite said housingopening and also covering said pocket means; said insulating meanshaving an opening in alignment with said pocket opening and operativelypositioned whereby a plug unit contact finger entering said pocket meansopening must first pass through said insulating means opening; saidinsulating means opening being smaller than said pocket means opening;each of said pocket means being formed by a ring-like member havingaligned slots therein; each of said conductors being entered into theslots of its associated pocket means ring-like member; said insulatingmeans being comprised of a resilient material; said insulating meansbeing spaced from said conductors at said pocket means by said ringlikemembers; said ring-like members being maintained in position solely bysaid conductors and said insulating means.

2. The combination comprising an electrical conductor and pocket meanshaving an opening constructed and operatively positioned to receive astab type contact which is electrically engageable with said conductor;insulating means covering said conductor for at least a portion of thelength thereof; said insulating means also covering said pocket means;said insulating means having an opening smaller in size than said pocketmeans opening and in alignment therewith; said pocket means being formedby a ring-like member having aligned slots; said conductor beingdisposed within said slots; said insulating means References Cited bythe Examiner UNITED STATES PATENTS 3/40 Harvey 339-22 5/42 La Jone339-21 Oarlson 33922 Doane 339111 Batcheller 339256 Rowe 33922 Johnstonet a1. 339-22 JOSEPH D. SEERS, Primary Examiner.

THOMAS J. HICKEY, Examiner.

2. THE COMBINATION COMPISING AN ELECTRICAL CONDUCTOR AND POCKET MEANSHAVING AN OPENING CONSTRUCTED AND OPERATIVELY POSITIONED TO RECEIVE ASTAB TYPE CONTACT WHICH IS ELECTRICALLY ENGAGEABLE WITH SAID CONDUCTOR;INSULATING MEANS COVERING SAID CONDUCTOR FOR AT LEAST A PORTION OF THELENGTH THEREOF; SAID INSULATING MEAND ALSO COVERING SAID POCKET MEANS;SAID INSULATING MEANS HAVING AN OPENING SMALLER IN SIZE THAN SAID POCKETMEANS BEING FORMED IN ALIGNMENT THEREWITH; SAID POCKET MEANS BEINGFORMED BY A RING-LIKE MEMBER HAVING ALIGNED SLOTS; SAID CONDUCTOR BEINGDISPOSED WITHIN SAID SLOTS; SAID INSULATING MEANS SPACED FROM SAIDCONDUCTOR AT SAID POCKET MEANS BY SAID RING-LIKE MEMBER; SAID RING-LIKEMEMBER BEING MAINTAINED IN POSITION SOLELY BY SAID CONDUCTOR AND SAIDINSULATING MEANS.